Optimization method of motor cogging torque and torque fluctuation and surface-mounted permanent magnet motor
阅读说明：本技术 电机齿槽转矩与转矩波动的优化方法及表贴式永磁电机 (Optimization method of motor cogging torque and torque fluctuation and surface-mounted permanent magnet motor ) 是由 王洪彦 于 2019-09-27 设计创作，主要内容包括：本发明公开一种电机齿槽转矩与转矩波动的优化方法及表贴式永磁电机,该电机齿槽转矩与转矩波动的优化方法包括：利用Maxwell仿真软件建立表贴式永磁电机仿真模型；基于表贴式永磁电机仿真模型对电机的永磁体厚度进行有限元仿真分析,以得到电机在不同永磁体厚度下齿槽转矩与转矩波动的第一优化结果；基于表贴式永磁电机仿真模型对电机的偏心距进行有限元仿真分析,以得到电机在不同偏心距下齿槽转矩与转矩波动的第二优化结果；根据电机在不同永磁体厚度下齿槽转矩与转矩波动的第一优化结果和电机在不同偏心距下齿槽转矩与转矩波动的第二优化结果,确定所述表贴式永磁电机的机械结构。本发明技术方案提高了表贴式永磁电机的运行性能。(The invention discloses a method for optimizing motor cogging torque and torque fluctuation and a surface-mounted permanent magnet motor, wherein the method for optimizing the motor cogging torque and the torque fluctuation comprises the following steps: establishing a surface-mounted permanent magnet motor simulation model by using Maxwell simulation software; finite element simulation analysis is carried out on the thickness of a permanent magnet of the motor based on a surface-mounted permanent magnet motor simulation model, so that a first optimization result of cogging torque and torque fluctuation of the motor under different thicknesses of the permanent magnet is obtained; carrying out finite element simulation analysis on the eccentricity of the motor based on the surface-mounted permanent magnet motor simulation model to obtain a second optimization result of cogging torque and torque fluctuation of the motor under different eccentricities; and determining the mechanical structure of the surface-mounted permanent magnet motor according to a first optimization result of the cogging torque and the torque fluctuation of the motor under different permanent magnet thicknesses and a second optimization result of the cogging torque and the torque fluctuation of the motor under different eccentricities. The technical scheme of the invention improves the running performance of the surface-mounted permanent magnet motor.)
1. The method for optimizing the cogging torque and the torque ripple of the motor is characterized by comprising the following steps of:
establishing a surface-mounted permanent magnet motor simulation model by using Maxwell simulation software;
finite element simulation analysis is carried out on the thickness of a permanent magnet of the motor based on a surface-mounted permanent magnet motor simulation model, so that a first optimization result of cogging torque and torque fluctuation of the motor under different thicknesses of the permanent magnet is obtained;
carrying out finite element simulation analysis on the eccentricity of the motor based on the surface-mounted permanent magnet motor simulation model to obtain a second optimization result of cogging torque and torque fluctuation of the motor under different eccentricities;
and determining the mechanical structure of the surface-mounted permanent magnet motor according to a first optimization result of the cogging torque and the torque fluctuation of the motor under different permanent magnet thicknesses and a second optimization result of the cogging torque and the torque fluctuation of the motor under different eccentricities.
2. The method for optimizing cogging torque and torque ripple of a motor according to claim 1, wherein the step of performing finite element simulation analysis on the thickness of the permanent magnet of the motor based on the surface-mounted permanent magnet motor simulation model to obtain a first optimization result of cogging torque and torque ripple of the motor under different thicknesses of the permanent magnet comprises:
under the conditions that the mechanical pole arc coefficient of the surface-mounted permanent magnet motor is kept unchanged and the surface-mounted permanent magnet motor is simulated to run in a no-load mode at a first preset rotating speed, the cogging torque peak value of the motor under different permanent magnet thicknesses is calculated according to a surface-mounted permanent magnet motor simulation model;
under the condition that the rotating speed of the surface-mounted permanent magnet motor is kept unchanged, inputting rated current to the motor based on a surface-mounted permanent magnet motor simulation model to obtain a rated torque wave peak value and a rated torque wave valley value of the motor permanent magnet under different thicknesses;
and substituting the rated torque wave peak value and the rated torque wave trough value into a first preset formula to obtain the torque fluctuation coefficient of the surface-mounted permanent magnet motor.
3. The method for optimizing cogging torque and torque ripple of a motor according to claim 2, wherein the step of substituting the peak value of the rated torque and the trough value of the rated torque into a first preset formula to obtain the torque ripple coefficient of the surface-mounted permanent magnet motor is specifically as follows:
by a first predetermined formula
4. The method for optimizing cogging torque and torque ripple of a motor according to claim 1, wherein the step of performing finite element simulation analysis on the thickness of the permanent magnet of the motor based on the surface-mounted permanent magnet motor simulation model to obtain the first optimization result of cogging torque and torque ripple of the motor under different thicknesses of the permanent magnet is preceded by:
calculating to obtain the no-load air gap flux density by using the surface-mounted permanent magnet motor simulation model;
carrying out fast Fourier transform on the no-load air gap flux density to obtain an air gap flux density fundamental wave amplitude and an air gap flux density harmonic amplitude;
under the condition that the surface-mounted permanent magnet motor operates at a second preset rotating speed in an idle load mode, substituting the air gap flux density fundamental wave amplitude and the air gap flux density harmonic amplitude into a second preset formula to obtain an idle load air gap flux density harmonic distortion rate of the surface-mounted permanent magnet motor;
and judging the optimization results of the thickness of the permanent magnet and the eccentricity of the permanent magnet according to the no-load air gap flux density harmonic distortion rate.
5. The method for optimizing cogging torque and torque ripple of a motor according to claim 4, wherein the step of substituting the amplitude of the airgap flux density fundamental and the amplitude of the airgap flux density harmonic into a second preset formula to obtain the no-load airgap flux density harmonic distortion of the surface-mounted permanent magnet motor is specifically as follows:
by a second predetermined formula
6. The method for optimizing cogging torque and torque ripple of a motor according to claim 5, wherein the step of performing finite element simulation analysis on the eccentricity of the motor based on the surface-mounted permanent magnet motor simulation model to obtain a second optimization result of cogging torque and torque ripple of the motor under different eccentricities comprises:
under the condition of keeping the mechanical pole arc coefficient of the surface-mounted permanent magnet motor unchanged and keeping the minimum air gap of the surface-mounted permanent magnet motor unchanged, the cogging torque and the torque fluctuation coefficient of the motor under different permanent magnet eccentricity are calculated according to a surface-mounted permanent magnet motor simulation model.
7. The method for optimizing cogging torque and torque ripple of a motor according to claim 1, wherein the magnetic core of the surface-mounted permanent magnet motor is made of cold-rolled non-oriented silicon steel.
8. The method for optimizing cogging torque and torque ripple of a motor according to claim 7, wherein the thickness of the permanent magnet of the surface-mounted permanent magnet motor ranges from 1mm to 4 mm.
9. The method for optimizing cogging torque and torque ripple of a motor according to claim 7, wherein the length of the eccentricity of the permanent magnet of the surface-mounted permanent magnet motor ranges from 5mm to 30 mm.
10. A surface-mounted permanent magnet motor, characterized in that it comprises a method for optimizing the cogging torque and the torque ripple of a motor according to any of claims 1 to 9.
Technical Field
The invention relates to the technical field of motors, in particular to a motor cogging torque and torque fluctuation optimization method and a surface-mounted permanent magnet motor.
Background
With the development of permanent magnet motors, servo motors for providing power for various robots and high-end industrial intelligent equipment are one of core functional components, and high-performance permanent magnet brushless torque servo motors are one of typical representatives. In the permanent magnet brushless torque servo motor, the rotating speed, the torque and the production cost are closely related to the number of poles, and the cogging torque in the permanent magnet brushless torque servo motor can directly influence the running performance of a generator, so that the cogging torque of the motor plays an important role in the motor.
Disclosure of Invention
The invention mainly aims to provide a method for optimizing cogging torque and torque fluctuation of a motor and a surface-mounted permanent magnet motor, and aims to improve the running performance of the surface-mounted permanent magnet motor.
In order to achieve the purpose, the method for optimizing the cogging torque and the torque fluctuation of the motor, which is provided by the invention, comprises the following steps:
establishing a surface-mounted permanent magnet motor simulation model by using Maxwell simulation software;
finite element simulation analysis is carried out on the thickness of a permanent magnet of the motor based on a surface-mounted permanent magnet motor simulation model, so that a first optimization result of cogging torque and torque fluctuation of the motor under different thicknesses of the permanent magnet is obtained;
carrying out finite element simulation analysis on the eccentricity of the motor based on the surface-mounted permanent magnet motor simulation model to obtain a second optimization result of cogging torque and torque fluctuation of the motor under different eccentricities;
and determining the mechanical structure of the surface-mounted permanent magnet motor according to a first optimization result of the cogging torque and the torque fluctuation of the motor under different permanent magnet thicknesses and a second optimization result of the cogging torque and the torque fluctuation of the motor under different eccentricities.
Optionally, the step of performing finite element simulation analysis on the thickness of the permanent magnet of the motor based on the surface-mounted permanent magnet motor simulation model to obtain a first optimization result of cogging torque and torque fluctuation of the motor under different thicknesses of the permanent magnet includes:
under the conditions that the mechanical pole arc coefficient of the surface-mounted permanent magnet motor is kept unchanged and the surface-mounted permanent magnet motor is simulated to run in a no-load mode at a first preset rotating speed, the cogging torque peak value of the motor under different permanent magnet thicknesses is calculated according to a surface-mounted permanent magnet motor simulation model;
under the condition that the rotating speed of the surface-mounted permanent magnet motor is kept unchanged, inputting rated current to the motor based on a surface-mounted permanent magnet motor simulation model to obtain a rated torque wave peak value and a rated torque wave valley value of the motor permanent magnet under different thicknesses;
and substituting the rated torque wave peak value and the rated torque wave trough value into a first preset formula to obtain the torque fluctuation coefficient of the surface-mounted permanent magnet motor.
Optionally, substituting the peak value of the rated torque and the trough value of the rated torque into a first preset formula to obtain a torque ripple coefficient of the surface-mounted permanent magnet motor specifically includes:
by a first predetermined formula
Optionally, the step of performing finite element simulation analysis on the thickness of the permanent magnet of the motor based on the surface-mounted permanent magnet motor simulation model to obtain a first optimization result of cogging torque and torque ripple of the motor under different thicknesses of the permanent magnet includes:
calculating to obtain the no-load air gap flux density by using the surface-mounted permanent magnet motor simulation model;
carrying out fast Fourier transform on the no-load air gap flux density to obtain an air gap flux density fundamental wave amplitude and an air gap flux density harmonic amplitude;
under the condition that the surface-mounted permanent magnet motor operates at a second preset rotating speed in an idle load mode, substituting the air gap flux density fundamental wave amplitude and the air gap flux density harmonic amplitude into a second preset formula to obtain an idle load air gap flux density harmonic distortion rate of the surface-mounted permanent magnet motor;
and judging the optimization results of the thickness of the permanent magnet and the eccentricity of the permanent magnet according to the no-load air gap flux density harmonic distortion rate.
Optionally, the step of substituting the air gap flux density fundamental amplitude and the air gap flux density harmonic amplitude into a second preset formula to obtain the no-load air gap flux density harmonic distortion rate of the surface-mounted permanent magnet motor specifically includes:
by a second predetermined formula
Optionally, the step of performing finite element simulation analysis on the eccentricity of the motor based on the surface-mounted permanent magnet motor simulation model to obtain a second optimization result of cogging torque and torque ripple of the motor under different eccentricities includes:
under the condition of keeping the mechanical pole arc coefficient of the surface-mounted permanent magnet motor unchanged and keeping the minimum air gap of the surface-mounted permanent magnet motor unchanged, the cogging torque and the torque fluctuation coefficient of the motor under different permanent magnet eccentricity are calculated according to a surface-mounted permanent magnet motor simulation model.
Optionally, the magnetic core of the surface-mounted permanent magnet motor is made of cold-rolled non-oriented silicon steel.
Optionally, the thickness of the permanent magnet of the surface-mounted permanent magnet motor ranges from 1mm to 4 mm.
Optionally, the length of the eccentricity of the permanent magnet of the surface-mounted permanent magnet motor ranges from 5mm to 30 mm.
The invention also provides a surface-mounted permanent magnet motor, which comprises the optimization method for the cogging torque and the torque fluctuation of the motor.
According to the technical scheme, a surface-mounted permanent magnet motor simulation model is established through Maxwell software, and the thickness and the eccentricity of a permanent magnet related to the surface-mounted permanent magnet motor simulation model are optimized so as to determine the mechanical structure of the surface-mounted permanent magnet motor. Further, after a surface-mounted permanent magnet motor simulation model is established, finite element simulation analysis is carried out on the thickness of a permanent magnet of the motor, so that the air gap flux density and the equivalent magnetic resistance are increased, and a first optimization result of cogging torque and torque fluctuation of the motor under different thicknesses of the permanent magnet is obtained; finite element simulation analysis is carried out on the eccentricity of the motor, the flux density of a no-load air gap is optimized, the flux density of the tooth part of the stator is uniformly distributed, and a second optimization result of cogging torque and torque fluctuation of the motor under different eccentricities is obtained, so that the purpose of reducing the cogging torque and the torque fluctuation of the motor is achieved. Because the no-load counter potential of the motor is increased along with the increase of the thickness of the permanent magnet of the motor, and the no-load counter potential of the motor is reduced along with the increase of the eccentricity of the permanent magnet of the motor, the optimization of the thickness and the eccentricity of the permanent magnet is carried out, the first optimization result and the second optimization result are combined and analyzed, and the optimized mechanical structure of the surface-mounted permanent magnet motor can be determined according to the optimization results of the cogging torque and the torque fluctuation after the permanent magnet motor is combined. The technical scheme of the invention improves the running performance of the surface-mounted permanent magnet motor.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a schematic flow chart illustrating an embodiment of a method for optimizing cogging torque of a motor according to the present invention;
FIG. 2 is a schematic view of a permanent magnet magnetic pole structure of a rotor structure of a surface-mounted permanent magnet motor;
FIG. 3 is a schematic diagram of the variation rate of the magnetic flux density harmonic wave of the air-carrying gap and the variation of the amplitude of the no-load back electromotive force fundamental wave with the thickness of the permanent magnet in the surface-mounted permanent magnet motor according to the present invention;
FIG. 4 is a schematic diagram of the variation rate of the magnetic flux density harmonic wave of the air-carrying gap and the variation of the amplitude of the no-load back electromotive force fundamental wave with the eccentricity of the permanent magnet in the surface-mounted permanent magnet motor according to the present invention;
fig. 5 is a schematic diagram of a curve of output torque varying with winding current in the surface-mounted permanent magnet motor according to the present invention.
The implementation and functional features of the object of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that, if directional indications (such as up, down, left, right, front, and back … …) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative positional relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly.
In addition, if there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
The invention provides an optimization method of motor cogging torque, which is applied to a surface-mounted permanent magnet motor. The method comprises the following steps according to the position of the permanent magnet magnetic pole of the rotor of the permanent magnet motor on the rotor: surface mount, in-cell, and claw pole types. The surface-mounted rotor structure is simple in manufacturing process, low in cost and wide in application, for the high-speed permanent magnet motor, some motor rotors adopt the surface-mounted motor rotors, the motor rotors generally comprise sheaths, permanent magnets, iron cores, rotating shafts and end plates, the iron cores are sleeved on the rotating shafts, the permanent magnets are located on the outer sides of the iron cores, the sheaths are located on the radial outer sides of the permanent magnets and wrap the permanent magnets, and the end plates are located on the two axial sides of the permanent magnets, so that eddy current loss can be reduced, and the strength of the sheaths.
In an embodiment of the present invention, as shown in fig. 1, the method for optimizing cogging torque and torque ripple of a motor includes:
s100, establishing a surface-mounted permanent magnet motor simulation model by using Maxwell simulation software;
step S200, carrying out finite element simulation analysis on the thickness of a permanent magnet of the motor based on a surface-mounted permanent magnet motor simulation model to obtain a first optimization result of cogging torque and torque fluctuation of the motor under different thicknesses of the permanent magnet;
step S300, carrying out finite element simulation analysis on the eccentricity of the motor based on the surface-mounted permanent magnet motor simulation model to obtain a second optimization result of cogging torque and torque fluctuation of the motor under different eccentricities;
and step S400, determining the mechanical structure of the surface-mounted permanent magnet motor according to a first optimization result of cogging torque and torque fluctuation of the motor under different permanent magnet thicknesses and a second optimization result of cogging torque and torque fluctuation of the motor under different eccentricity.
In this embodiment, the surface-mounted permanent magnet motor includes a stator and a rotor, the stator is provided with a plurality of teeth, a slot is formed between adjacent teeth, the rotor is provided with a plurality of pairs of magnetic shoes, the number of poles of the permanent magnet in the surface-mounted permanent magnet motor is referred to as a pole for short, the number of poles is the number of magnetic shoes, and N and S in one magnetic shoe calculate two poles. The magnetic shoe is mainly used in a permanent magnet direct current motor, and is different from an electromagnetic motor which generates a magnetic potential source through a magnet exciting coil, and the permanent magnet motor generates a constant magnetic potential source through a permanent magnet material. The permanent magnetic shoe replaces the electric excitation, which can make the motor simple in structure, light in weight, small in volume, reliable in use, etc.
In this embodiment, a surface-mounted permanent magnet motor simulation model is first established by Maxwell simulation software, and the thickness and the eccentricity of a permanent magnet involved in the surface-mounted permanent magnet motor simulation model are optimized to determine the mechanical structure of the surface-mounted permanent magnet motor. Further, as shown in fig. 2, a schematic diagram of a magnetic pole structure of a permanent magnet in a rotor structure of a surface-mounted permanent magnet motor is shown, so that the implementation of a permanent magnet bonding process and the reduction of processing cost are facilitated, the permanent magnet adopts an equal-width design, a bottom circle of the permanent magnet is tightly attached to a hollow shaft of the rotor, namely, the radius of an inner circle of the permanent magnet, so that an inter-pole air gap is enlarged, an equivalent mechanical pole arc coefficient is reduced, a total magnetic flux is reduced, and a force performance. Therefore, parameters such as the eccentricity h of the permanent magnet magnetic pole, the thickness hm of the permanent magnet and the like need to be subjected to simulation optimization analysis by means of finite element calculation, and finally, the parameter values are determined so as to determine the mechanical structure of the permanent magnet magnetic pole of the surface-mounted permanent magnet motor rotor structure.
In the above embodiment, for the thickness of the permanent magnet of the surface-mounted permanent magnet motor, the thickness of the permanent magnet is linearly related to the peak value of the cogging torque, the peak value of the rated torque, the valley value of the rated torque of the permanent magnet motor, and the thickness of the permanent magnet is linearly related to the no-load back electromotive force. The thickness of the permanent magnet is optimized based on a surface-mounted permanent magnet motor simulation model, so that the air gap flux density and the equivalent magnetic resistance of the permanent magnet motor pair are increased, and a first optimization result of cogging torque and torque fluctuation of the motor under different permanent magnet thicknesses is obtained. The cogging torque and torque fluctuation curve fluctuation data under different permanent magnet thicknesses are obtained, and the obtained curve fluctuation data are compared and screened, so that the optimized mechanical structure of the surface-mounted permanent magnet motor can be determined, and the running performance of the surface-mounted permanent magnet motor is improved.
For the permanent magnet eccentricity of the surface-mounted permanent magnet motor, the linear relation between the permanent magnet eccentricity and the air gap flux density fundamental wave amplitude, the air gap flux density harmonic amplitude and the no-load air gap flux density harmonic distortion rate and the linear relation between the permanent magnet eccentricity and the no-load back electromotive force are adopted. The method has the advantages that the eccentricity of the permanent magnet is optimized based on a surface-mounted permanent magnet motor simulation model, unequal air gaps of the permanent magnet motor are realized, the flux density of a no-load air gap is optimized, the flux density of a stator tooth part of the permanent magnet motor is uniformly distributed, and a second optimization result of cogging torque and torque fluctuation of the motor under different eccentricities is obtained. The cogging torque and torque fluctuation curve fluctuation data under different permanent magnet eccentricity are obtained, and the obtained curve fluctuation data are compared and screened, so that the optimized mechanical structure of the surface-mounted permanent magnet motor can be determined, and the running performance of the surface-mounted permanent magnet motor is improved.
For the optimization of the thickness and the eccentricity of the permanent magnet based on the surface-mounted permanent magnet motor simulation model, according to the linear relation between the no-load back electromotive force and the thickness of the permanent magnet and the eccentricity of the permanent magnet motor and the linear relation between the no-load back electromotive force and the torque fluctuation of the permanent magnet motor, the optimized mechanical structure of the surface-mounted permanent magnet motor is determined by comparing and screening the linear relation data obtained by the combination according to the first optimization result of the cogging torque and the torque fluctuation of the permanent magnet under different thicknesses and the second optimization result of the cogging torque and the torque fluctuation of the permanent magnet under different eccentricities, so that the running.
In the embodiment, the thickness and the eccentricity of the permanent magnet of the surface-mounted permanent magnet motor are optimized, the mechanical structure design of the permanent magnet motor is determined, and the cogging torque and the torque fluctuation of the motor are reduced; meanwhile, the amplitude of the no-load air gap flux density fundamental wave and the amplitude of the no-load air gap flux density harmonic wave of the permanent magnet motor can be reduced, and the relation between the no-load back electromotive force and the thickness and the eccentricity of the permanent magnet motor is utilized; and under the condition of different permanent magnet thicknesses, observing the size of the cogging torque by using the winding current of the permanent magnet motor and the no-load output torque of the permanent magnet motor. The no-load air gap flux density harmonic distortion rate is reduced, so that the cogging torque and the torque fluctuation of the permanent magnet motor are reduced.
According to the scheme, a surface-mounted permanent magnet motor simulation model is established through Maxwell software, and the thickness and the eccentricity of a permanent magnet related to the surface-mounted permanent magnet motor simulation model are optimized so as to determine the mechanical structure of the surface-mounted permanent magnet motor. Further, after a surface-mounted permanent magnet motor simulation model is established, finite element simulation analysis is carried out on the thickness of a permanent magnet of the motor, so that the air gap flux density and the equivalent magnetic resistance are increased, and a first optimization result of cogging torque and torque fluctuation of the motor under different thicknesses of the permanent magnet is obtained; finite element simulation analysis is carried out on the eccentricity of the motor, the flux density of a no-load air gap is optimized, the flux density of the tooth part of the stator is uniformly distributed, and a second optimization result of cogging torque and torque fluctuation of the motor under different eccentricities is obtained, so that the purpose of reducing the cogging torque and the torque fluctuation of the motor is achieved. Because the no-load counter potential of the motor is increased along with the increase of the thickness of the permanent magnet of the motor, and the no-load counter potential of the motor is reduced along with the increase of the eccentricity of the permanent magnet of the motor, the optimization of the thickness and the eccentricity of the permanent magnet is carried out, the first optimization result and the second optimization result are combined and analyzed, and the optimized mechanical structure of the surface-mounted permanent magnet motor can be determined according to the optimization results of the cogging torque and the torque fluctuation after the permanent magnet motor is combined. The technical scheme of the invention improves the running performance of the surface-mounted permanent magnet motor.
In an embodiment, the step of performing finite element simulation analysis on the thickness of the permanent magnet of the motor based on the surface-mounted permanent magnet motor simulation model to obtain a first optimization result of cogging torque and torque ripple of the motor under different thicknesses of the permanent magnet includes:
under the conditions that the mechanical pole arc coefficient of the surface-mounted permanent magnet motor is kept unchanged and the surface-mounted permanent magnet motor is simulated to run in a no-load mode at a first preset rotating speed, the cogging torque peak value of the motor under different permanent magnet thicknesses is calculated according to a surface-mounted permanent magnet motor simulation model;
under the condition that the rotating speed of the surface-mounted permanent magnet motor is kept unchanged, inputting rated current to the motor based on a surface-mounted permanent magnet motor simulation model to obtain a rated torque wave peak value and a rated torque wave valley value of the motor permanent magnet under different thicknesses;
and substituting the rated torque wave peak value and the rated torque wave trough value into a first preset formula to obtain the torque fluctuation coefficient of the surface-mounted permanent magnet motor.
It can be understood that in the scheme, under the conditions that the mechanical pole arc coefficient of the surface-mounted permanent magnet motor is kept unchanged and the surface-mounted permanent magnet motor is simulated to run in a no-load mode at a first preset rotating speed, the peak value of the cogging torque of the motor under different permanent magnet thicknesses is obtained through simulation model calculation. The method is characterized in that fluctuation data of cogging torque and permanent magnet thickness of the surface-mounted permanent magnet motor under the condition that the thicknesses of the permanent magnets of the surface-mounted permanent magnet motor are different are obtained through simulation model calculation. The thickness of the permanent magnet under low cogging torque is selected by screening cogging torque and permanent magnet thickness fluctuation change data.
In this embodiment, substituting the peak value of the rated torque and the trough value of the rated torque into a first preset formula to obtain a torque ripple coefficient of the surface-mounted permanent magnet motor specifically includes:
by a first predetermined formula
It can be understood that in the scheme, under the condition that the first preset rotating speed is kept unchanged, the rated current is input to the motor based on the surface-mounted permanent magnet motor simulation model, and the rated torque wave peak value and the rated torque wave valley value of the motor permanent magnet under different thicknesses are obtained. The method is characterized in that the torque fluctuation data and the fluctuation change data of the thickness of the permanent magnet of the surface-mounted permanent magnet motor are obtained through simulation model calculation under the condition that the thicknesses of the permanent magnets of the surface-mounted permanent magnet motor are different. The thickness of the permanent magnet under low torque fluctuation is selected by screening the data of the torque fluctuation and the thickness fluctuation change of the permanent magnet.
In the above embodiment, the permanent magnet thickness when both the cogging torque and the torque ripple are low is selected by combining the cogging torque of the surface-mounted permanent magnet motor, the torque ripple of the surface-mounted permanent magnet motor, and the ripple variation data of the permanent magnet thickness. Therefore, the optimized mechanical structure of the surface-mounted permanent magnet motor is determined, and the running performance of the surface-mounted permanent magnet motor is improved.
It should be noted that the first preset rotation speed is 1r/min for no-load operation, and the first preset rotation speed may also be 2r/min, 3r/min, and the like, which is not limited herein.
For the above embodiment, when the first preset rotation speed is maintained at 1r/min for idle operation, there are the following experimental data regarding the thickness of the permanent magnet, the cogging torque and the torque ripple, as shown in table 1:
TABLE 1
In an embodiment, the step of performing finite element simulation analysis on the thickness of the permanent magnet of the motor based on the surface-mounted permanent magnet motor simulation model to obtain a first optimization result of cogging torque and torque ripple of the motor under different thicknesses of the permanent magnet includes:
calculating to obtain the no-load air gap flux density by using the surface-mounted permanent magnet motor simulation model;
carrying out fast Fourier transform on the no-load air gap flux density to obtain an air gap flux density fundamental wave amplitude and an air gap flux density harmonic amplitude;
under the condition that the surface-mounted permanent magnet motor operates at a second preset rotating speed in an idle load mode, substituting the air gap flux density fundamental wave amplitude and the air gap flux density harmonic amplitude into a second preset formula to obtain an idle load air gap flux density harmonic distortion rate of the surface-mounted permanent magnet motor;
and judging the optimization results of the thickness of the permanent magnet and the eccentricity of the permanent magnet according to the no-load air gap flux density harmonic distortion rate.
In this embodiment, the fast fourier transform means that a certain function satisfying a certain condition is expressed as a trigonometric function (sine and/or cosine function) or a linear combination of their integrals. In different fields of research, fast fourier transforms have many different variant forms, such as continuous fourier transforms and discrete fourier transforms. It is a method of analyzing a signal, and components of the signal may be analyzed, or the signal may be synthesized using these components. Many waveforms can be used as components of the signal, such as sine waves, square waves, sawtooth waves, etc., and fast fourier transforms use sine waves as components of the signal. In the scheme, the no-load air gap flux density is decomposed into an air gap flux density fundamental wave amplitude and an air gap flux density harmonic wave amplitude through fast Fourier transform, the air gap flux density fundamental wave amplitude and the air gap flux density harmonic wave amplitude can be substituted into a second preset formula, and the no-load air gap flux density harmonic wave distortion rate of the surface-mounted permanent magnet motor is calculated, so that the linear relations between the thickness of a permanent magnet of the surface-mounted permanent magnet motor and the no-load air gap flux density harmonic wave distortion rate and the no-load back electromotive force respectively can be embodied, and the linear relations between the eccentricity of the permanent magnet and the no-load air gap flux density harmonic wave distortion rate and the no-load back electromotive force respectively.
In the above embodiment, the step of substituting the amplitude of the air gap flux density fundamental wave and the amplitude of the air gap flux density harmonic wave into a second preset formula to obtain the no-load air gap flux density harmonic wave distortion rate of the surface-mounted permanent magnet motor specifically includes:
by a second predetermined formula
It can be understood that k ═ 2 in the present scheme represents that the air gap flux density harmonic amplitude is calculated from the second time, and under the condition of simulating the surface-mounted permanent magnet motor to operate in no-load at the second preset rotation speed, the no-load air gap flux density harmonic distortion rate and the no-load back-emf fundamental wave amplitude of the motor permanent magnet under different thicknesses are obtained, as shown in fig. 3, that is, the curve diagram of the variation of the air carrier air gap flux density harmonic distortion rate and the no-load back emf fundamental wave amplitude with the thickness of the permanent magnet in the surface-mounted permanent magnet motor is shown. As can be seen from fig. 3, as the thickness of the permanent magnet increases, the no-load air gap flux density harmonic distortion rate of the surface-mounted permanent magnet motor decreases, and the no-load back electromotive force fundamental amplitude of the surface-mounted permanent magnet motor increases.
In addition, the no-load air gap flux density harmonic distortion rate and the no-load back-emf fundamental wave amplitude of the motor permanent magnet under different eccentricity can also be obtained, as shown in fig. 4, that is, the curve diagram of the variation of the no-load air gap flux density harmonic distortion rate and the no-load back-emf fundamental wave amplitude with the eccentricity of the permanent magnet in the surface-mounted permanent magnet motor is shown. As can be seen from fig. 4, as the eccentricity of the permanent magnet increases, the no-load air gap flux density harmonic distortion rate of the surface-mounted permanent magnet motor and the no-load back electromotive force fundamental amplitude of the surface-mounted permanent magnet motor decrease.
Further, the step of performing finite element simulation analysis on the eccentricity of the motor based on the surface-mounted permanent magnet motor simulation model to obtain a second optimization result of cogging torque and torque fluctuation of the motor under different eccentricities includes:
under the condition of keeping the mechanical pole arc coefficient of the surface-mounted permanent magnet motor unchanged and keeping the minimum air gap of the surface-mounted permanent magnet motor unchanged, the cogging torque and the torque fluctuation coefficient of the motor under different permanent magnet eccentricity are calculated according to a surface-mounted permanent magnet motor simulation model.
It can be understood that under the condition that the eccentricity of the permanent magnet of the surface-mounted permanent magnet motor is different, the cogging torque and the torque fluctuation of the surface-mounted permanent magnet motor and the fluctuation change data of the thickness of the permanent magnet are obtained through calculation of a simulation model, and the eccentricity of the permanent magnet under the condition that the cogging torque and the torque fluctuation are lower is selected through screening the cogging torque and the torque fluctuation and the fluctuation change data of the thickness of the permanent magnet.
In the above embodiment, the thickness of the permanent magnet when the cogging torque and the torque fluctuation are low is selected by combining the cogging torque of the surface-mounted permanent magnet motor, the torque fluctuation of the surface-mounted permanent magnet motor, and the fluctuation change data of the eccentricity of the permanent magnet. Therefore, the optimized mechanical structure of the surface-mounted permanent magnet motor is determined, and the running performance of the surface-mounted permanent magnet motor is improved.
It should be noted that the second preset rotation speed is 1000r/min for no-load operation, and the first preset rotation speed may also be 900r/min, 1200r/min, etc., which is not limited herein.
For the above embodiment, when the second preset rotation speed is maintained at 1000r/min for idle operation, there are the following experimental data regarding the thickness of the permanent magnet, the cogging torque and the torque ripple, as shown in table 2:
permanent magnet eccentricity h (mm)
Cogging torque Tcog(mN·m)
Torque ripple KTb(％)
5
52.65
4.1
10
48.3
3.93
15
65.75
3.31
20
78.96
2.98
25
84.03
2.53
30
52.2
2.13
TABLE 2
In the above embodiment, the magnetic core of the surface-mount permanent magnet motor is made of cold-rolled non-oriented silicon steel. Further, the thickness range of the permanent magnet of the surface-mounted permanent magnet motor is 1mm-4 mm. It is understood that the thickness of the permanent magnet of the surface-mount permanent magnet motor may be 1mm, 1.5mm, 4mm, etc., without limitation.
In this embodiment, the length range of the eccentricity of the permanent magnet of the surface-mounted permanent magnet motor is 5mm to 30 mm. It is understood that the eccentricity of the permanent magnet of the surface-mount permanent magnet motor may be 5mm, 10mm, 30mm, etc., and is not limited thereto.
For the above embodiment, it is conceivable that there are also factors that affect the linearity of the output torque and current of the permanent magnet motor, and the linearity of the torque and current of the permanent magnet motor also affects the performance of the surface-mounted permanent magnet motor. For the torque current linearity of the permanent magnet motor, the saturation degree of the magnetic density of the iron core of the permanent magnet motor is one of important factors. In general, in order to improve the performance of the motor, cold-rolled non-oriented silicon steel material is adopted, and when the thickness of the permanent magnet is a preset thickness, the lamination coefficient and the saturation point of the magnetization curve under the thickness are determined according to the actual condition. After the permanent magnet motor is electrified with a certain degree of torque current, the magnetic density of the stator core can locally reach or exceed the saturation point of the magnetization curve to cause saturation, and if the torque current is applied again, the output torque and the torque current are not in a linear relation any more, so that the linearity of the output torque and the current is influenced.
When the motor runs at a first preset rotating speed of 1r/min, 2A-38A current is introduced into the winding, and the thickness hm of the permanent magnet is 2.5mm and 4mm respectively, a curve of the output torque value of the motor and the ideal torque current is calculated in a simulation mode and is shown in figure 5.
The invention also provides a surface-mounted permanent magnet motor, which comprises the optimization method for the cogging torque and the torque fluctuation of the motor. The specific steps of the method for optimizing the cogging torque and the torque ripple of the motor refer to the above embodiments, and the surface-mounted permanent magnet motor adopts all technical solutions of all the above embodiments, so that the method at least has all beneficial effects brought by the technical solutions of the above embodiments, and details are not repeated herein.
The above description is only an alternative embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
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